Finance
Estimate how many months your cash covers essential spending when income drops.
Results update as you type. No calculate button. All calculations run locally in your browser.
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| Amount | |
|---|---|
| Usable cash | — |
| Monthly shortfall | — |
| Buffer amount | — |
| Total cash | — |
Bars are scaled to total cash. The buffer is money you choose not to spend even in an emergency; usable cash is what actually funds the runway.
| Buffer kept back | Usable cash | Runway |
|---|
Each row recomputes usable cash as cash times (1 minus buffer) and divides by the same monthly shortfall.
Monthly shortfall = monthly expenses − monthly emergency income. Usable cash = cash × (1 − buffer%). Runway = usable cash ÷ monthly shortfall, when the shortfall is positive. If income covers expenses, the runway is not limited by cash.
Cash $120,000 with a 10% buffer: usable cash is $120,000 × 90% = $108,000, kept back $12,000. Monthly shortfall is $15,000 − $5,000 = $10,000, so runway is $108,000 ÷ $10,000 = 10.8 months.
Expenses and emergency income are assumed flat every month, with no interest earned on cash, no new debts, no one-off costs, and no change in the buffer. Real emergencies are lumpy: a single large bill shortens the runway more than the smooth monthly average suggests.
Money you deliberately do not spend: a floor for non-negotiable costs, a deposit, or a reserve for the month after the emergency. A larger buffer shortens the runway but leaves a cushion.
Then the shortfall is zero or negative and cash is not being drained: the runway is not limited by cash on these figures. The calculator says so rather than dividing by zero.
Bare-minimum essential spending gives the true emergency runway. Normal spending gives a shorter, more conservative figure; run both and compare.
Not here. Interest on a cash pile is small relative to monthly spending, and assuming none keeps the estimate conservative.
That depends on your situation and is not a number this calculator prescribes. Common planning horizons are a few months to a year; the sensitivity table above shows what each buffer level costs in months.
Results are estimates only and do not constitute professional advice.